This invention relates to a device for detecting infrared rays utilizing the pyroelectric effect and methods for manufacturing the same.
Generally, pyroelectric materials are used in pyroelectric detectors for detecting infrared rays by utilizing the pyroelectric effect. However, if the heat capacity of a the pyroelectric material is great, the pyroelectric material cannot respond to a fast change in the energy of infrared rays. Therefore, various techniques are used in the prior art to reduce the heat capacity of pyroelectric materials. For example, by reducing the thickness of the pyroelectric material to about 30-50 .mu.m, heat capacity is reduced.
In the prior art, heat capacity also is reduced by exposing the pyroelectric material to air and mounting the pyroelectric material on a heat insulated substrate. A technique for exposing the pyroelectric material to air is shown in FIG. 1. A piezoelectric crystal 3 is mounted on a stand 5 by the wires 4 and 4'. The electrode 1 for receiving infrared rays and the shield electrode 2 are formed on different sides of the piezoelectric crystal 3. Although heat capacity is reduced, the pyroelectric detector shown in FIG. 1 is not reliable or durable; it also is very difficult to manufacture and treat the pyroelectric detector because the pyroelectric crystal 3 is so thin.
Another prior art technique is shown in FIG. 2. The shield electrode 2, which is formed on one side of piezoelectric crystal 3, is connected to the heat insulated substrate 6 which is in turn mounted on the stand 5. The pyroelecric detector shown in FIG. 2 has the disadvantage that it is difficult to connect wire 4 to the shield electrode 2.
Another known structure is shown in FIG. 3. This structure is described in Japanese patent publication No. 12272/1976 (Tokkosho). The shield electrode 2, which is mounted on one side of piezoelectric crystal 3, is formed around a heat insulated substrate 6 and mounted on stand 5 by conductive glue. The heat insulated substrate 6 is covered by an SnO2 film 7 so it is unnecessary to connect the shield electrode 2 to stand 5 by wire 4. However, because the piezoelectric crystal 3 is mounted on the substrate 6, the heat capacity is great which prevents the detector from responding to fast changes in the energy of infrared rays. It also is difficult to manufacture and treat the detector shown in FIG. 3 because it is necessary to mount a very thin pyroelectric crystal. In FIGS. 1-3, electrode 1 is connected to lead terminal 8 by wire 4'. Terminal 8 is insulated from stand 5 by insulation 9.